Why does Zyra's snare still have a cast time?

Zyra's snare is slow, yes, but its hitbox is deceptively wider and longer than it appears. You simply have to practice with her and know when to throw out her spells. Plus, remember to throw seeds out when you cast your E or Q so you still have a chance to harass and/or slow your opponent even if you miss your original spell.

cast time? you mean travel speed? her snare cast time is instant but travels towards the direction you click. lol